Like all biological functions, the immune system places demands on an organism and a new study in the journal PLoS ONE has found the highly active immune systems of some endangered Galapagos sea lions are stressing the animals to the point of starvation.

Apparently humans aren’t the only ones who enjoy a brain teaser every now and again, as newly published research has revealed solving puzzles also seems to be a source of gratification for chimpanzees.

Published today by the Zoological Society of London (ZSL) and University of Cambridge, the study reveals that male hihi birds develop more colorful and attractive breeding feathers if they receive a nest diet rich in carotenoids – natural pigments found mainly in fruit and vegetables.